1. Field of the Invention
This invention relates to a digital signal processing apparatus for processing digital signals, such as digital audio signals.
2. Description of the Prior Art
Recently, it has become customary to perform various digital signal processing operations, including numerical computations, such as computations for digital filters, fast Fourier transform (FFT) or correlative functions, for digital signals such as digitized audio or video signals, on a real-time basis, and a variety of digital signal processing apparatus, known as DSP, have been evolved to perform such real time operations. In general, a DSP includes a computing block to perform arithmetic operations, such as multiplication or addition, an instruction RAM for writing a microprogram stating the signal processing sequence, a data RAM for transient data storage, and a coefficient RAM for storing coefficients employed in the arithmetic operation in the computing block.
Thus, under the control of the microprogram, written in the instruction RAM, data are read out from the data RAM and the coefficient RAM, and an arithmetic operation is performed by the computing block for processing digital signals.
However, since a conventional DSP is mainly designed for high-speed signal processing, it is customary to perform a single job on the DSP. When plural jobs are executed in parallel, especially at different speeds, the program contents become complicated in order to realize such parallel processing in one program on a one-chip DSP, otherwise wasteful execute cycles may be generated at the transition point from one job to another.
On the other hand, when plural jobs are executed using plural DSPs, data exchange between the DSPs becomes complicated. When the DSPs are connected in series objectionable time delays may be produced. Moreover, the use of plural DSPs results in an increased mounting space and elevated costs.